(1) Field of the Invention
This invention relates to an anti-corrosion ceramic member, more particularly to an anti-corrosion ceramic member favorably usable for a member of equipment for manufacturing a semiconductor, such as thermal CVD equipment.
(2) Related Art Statement
With enlarging the capacity of VLSIs, the VLSIs have come to be increasingly micro-processed, which have enlarged uses of processes requiring chemical reactions. Particularly in semiconductor-manufacturing equipment requiring a super clean condition, a halogen-based corrosion gas such as a chlorine-based gas or a fluorine-based gas is used as a deposition gas, an etching gas or a cleaning gas.
In manufacturing equipment for a semiconductor, such as a CVD equipment, as a heater to heat a substance contact with such a corrosion gas, the halogen-based corrosion gas such as CiF3, NF3, CF4, HF or HCl is used as a semiconductor cleaning gas after deposition. Moreover, during the deposition, a halogen-based corrosion gas such as WF6, SiH2, or Cl2 is employed as a gas for forming a film.
Each of the members composing the semiconductor-manufacturing equipment is made of a ceramic material such as alumina or aluminum nitride. Accordingly when these members are exposed to and contacted with the above halogen-based corrosion gas at a high temperature, the surfaces of the members are corroded and the thus corroded portions of the surface are peeled off from the members in the form of particles.
The above particles are deposited on a substrate arranged in the semiconductor-manufacturing equipment, which results in poor insulation and poor conductivity, making the resulting semiconductor porous.
Considering the above problem, NGK Insulators, Ltd. disclosed in Japanese patent application No. 3-150932 (filed on May 28, 1991) and Japanese patent application No. 4-58727 (filed on Feb. 13, 1992), etc. that a sintered body of aluminum nitride with a layer of aluminum fluoride on its surface has a high corrosion resistance against a plasma of a halogen-based corrosion gas.
However when a ceramic member having a fluoride layer such as aluminum fluoride on its surface is employed as a member for the semiconductor-manufacturing equipment as mentioned above, the fluoride layer may be peeled off due to rapid changes in temperature inside the semiconductor manufacturing equipment. The peeled fluoride is in the form of particles. When the fluoride particles are deposited on the substrate, the deposited fluoride particles make the thus obtained semiconductor unacceptable.
It is an object of the present invention to provide an anti-corrosion ceramic member having a surface layer of a fluoride with good adherence to a substrate and having a high corrosion resistance against a plasma of a halogen-based corrosion gas.
This invention relates to an anti-corrosion ceramic member comprising a substrate made of a ceramic material, a surface layer made of a fluoride and formed on the substrate, and an intermediate layer formed between the substrate and the surface layer and comprising the ceramic material of the substrate and the fluoride.
The anti-corrosion ceramic member of this invention has a fluoride surface layer on its surface, so that the member has a high corrosion resistance against the halogen-based corrosion gas plasma.
Since the intermediate layer, which comprises the ceramic material of the substrate and the fluoride, is formed between the ceramic substrate and the fluoride surface layer, the adherence of the fluoride surface layer to the ceramic substrate is improved. Consequently the fluoride surface layer is not peeled off of the ceramic member even with rapid changes in temperature, which can prevent the disorders of the semiconductor which occur due to occurrence of particles being peeled from the fluoride surface layer.
The reason why the fluoride surface layer is not peeled off by forming the above intermediate layer is not clear, but it may be as follows.
That is, if rapid changes in temperature happen, large thermal stress is generated between the substrate of such as alumina and a fluoride due to a difference in heat expansion therebetween. However when the above intermediate layer made of the material composing the ceramic substrate and the fluoride is formed between the substrate and the fluoride, its act as a buffer layer to reduce the difference in the heat expansion therebetween and prevent the occurrence of rapid thermal stress, so that the adherence of the fluoride surface layer to the substrate is improved and thereby the fluoride surface layer is not peeled off.